This paper presents the bit-error-rate (BER) performance of an upwards-expandable spectral and power efficient quasi-synchronous multi-layer-modulated (MLM) four-dimensional super-orthogonal wideband code-division multiple access (QS-4D-SO-WCDMA) modem, suitable for application in next generation WLAN and wireless cellular systems. The unique combination of the 4D-WCDMA modem configuration and super-orthogonal families of root-of-unity filtered (RUF) constant-envelope generalized-chirp-like complex spreading sequences (SO-CE-GCL-CSS), renders a spectrally and power efficient output signal with data throughput rates equivalent to that of a 16-ary quadrature amplitude modulated (16-QAM) WCDMA modulation scheme, but with the BER performance equivalent to that of BPSK/QPSK in both AWGN and fading multipath channel scenarios.